The police do, too, and that's how they uncovered Justin Ross Harris' apparent double life of sexting and his penchant for videos about death.

Police believe Harris, who also is charged with child cruelty, intentionally killed his son, Cooper. Harris has told police he was supposed to drive his son to day care the morning of June 18 but drove to work without realizing that his son was strapped into a car seat in the back. Cooper was in the car for seven hours before his father said he realized he was there.

During Harris' probable cause hearing Thursday, Cobb County Police Detective Phil Stoddard testified that Harris was sexting with several women on the day of his son's death and he had accessed websites advocating "child free" and searched "how to survive prison" before Cooper died.

Harris' computers were discussed during the hearing.

"We talked a little bit about these computers; have you guys done examinations on these computers?" asked Cobb County prosecutor Chuck Boring of Stoddard.

"We have," Stoddard responded.

"Are you finished with your examination of these computers?"

"We've only scratched the surface," Stoddard answered.

"These experts in law enforcement have been trained in computer forensics," said Greg Evans of Hi Tech Crime Solutions. "They have the best software in the world that will go in and go through each sector. It may not take a day. It can take a month; it can take a week; or it can take 6 months depending on how much data you have on there."

Harris had access to at least three computers. And police said it's clear he was covering his tracks on all of them.

But in cyberspace, "delete" doesn't mean "gone."

"When you delete a file on your computer, it's still there," explained computer security expert Evans. "It just renames the sector to say this is just unused space right now. And then something else can write over top of it."

Evans said the same applies to your tablets and cellphones. The files are there and not there. At the same time.

"People think 'Well, this is a cellphone. Once I delete a picture or text message or my contacts, it's gone,'" Evans said. "No. Even when you hit 'reset' on your phone, that information is still stored on that hard drive."

At the end of Thursday's hearing, Cobb Magistrate Judge Frank Cox ruled there was enough evidence to send the murder case to the grand jury.